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sive from contamination not only with their faeces but also with
the secretion from their scent glands, and the cockroach is strongly
suspected of transmitting to man a number of pathogenic organisms
especially those of an enteric nature.
Cockroaches shun the light and are most active during the night.
Warmth, moisture, darkness and close proximity to food supplies
constitute favourable conditions for breeding.
Fifty-eight complaints were received concerning this pest and
thorough investigation and treatment with Dieldrin Concentrate
resulted in the infestations being considerably reduced. In all, 57
treatments were effected involving 367 rooms.
Clover Mite.—Four complaints were received, mainly from tenants
in blocks of flats in various parts of the Borough, concerning
small red or dark brown insects (Bryobia praetiosa) found moving
over walls and windows. Treatment consisted of spraying 3 rooms
and 4 exterior surfaces with Dieldrin Concentrate which produced
satisfactory results.
Wasps.—Complaints received implicated three types, the
Common, the German and the Tree wasp. (Vespula vulgaris, V.
germanica and V. sylvestris.)
Fear of the wasp is often misplaced for they rarely sting unless
they are roused or frightened and, contrary to popular belief, wasps
are not entirely harmful for in spring and early summer they feed
mainly on insects, many of which are themselves injurious. However,
after mid-summer their diet becomes more vegetarian and the
workers feed on ripening fruit and other sweet substances, thus
effecting serious damage in orchards, sugar warehouses, grain
factories, etc., where they cause considerable wastage of goods. In
houses they become a nuisance during cooking and at meal times
and it is conceivable that they are instrumental in the spread of
food poisoning.
The queen wasp, the only survivor from the previous year's
colony, emerges from hibernation in the spring to choose a site for
nesting, usually in cavity walls, lofts, under roof tiles or other sites
which evoke a certain ingenuity on the part of the disinfestors in
order satisfactorily to deal with the nuisance.
Two hundred and sixty-five complaints regarding this pest were
received and during the year some 141 nests were destroyed,
mainlv bv means of Gammexane powder or Dieldrin Concentrate.
Many other types of infestation were encountered and the
following is a list of the treatments which were carried out in connection
therewith.